A trend in the construction industry has been to utilize smaller, more versatile machinery on the job-site. For example, mini-excavators and skid-steer loaders are often used to perform a variety of tasks. In many cases, a skid-steer loader or mini-excavator is equipped with an attachment for performing a particular task. Such attachments are typically powered by an auxiliary hydraulic circuit on the skid-steer loader or mini-excavator. Numerous attachments exist for performing a variety of tasks. For example, attachments exist for allowing a skid-steer loader to be used as a backhoe, an earth auger, an angle broom, a drop hammer, a snowplow, a brush saw, etc.
When using some types of attachments, it is often desirable to use a stabilizer system to raise the vehicle's wheels off of the ground in order to provide a more stable operating foundation. Typical stabilizer systems include one or more stabilizer legs that are lowered and raised by hydraulic piston-cylinder assemblies respectively to lift and lower the vehicle relative to the ground.
When selecting a stabilizer system for a vehicle, design parameters include, among other things, the maximum load the stabilizer system must be able to accommodate, and the rate at which the stabilizer legs can be extended and/or retracted. As will be appreciated, for a stabilizer system having a pump of a given size, as the load rating of the system increases the rate at which the stabilizer legs can be extended and retracted typically decreases. Accordingly, as the load capacity increases the stabilizer system takes longer to deploy thereby making the system less convenient to use.
One way to increase the load rating and maintain the rate of extension and retraction is to use a more powerful pump. However, using a more powerful pump usually means increased costs and may also require more space.
Another problem that arises when using piston-cylinder assemblies having a relatively large diameter piston rod, as is often the case in a vehicle stabilizer system where heavy loads are encountered. In such assemblies, the amount of fluid displaced from the piston side chamber of the cylinder during retraction of the piston rod is considerably greater than the amount of fluid flowing into the rod side chamber of the cylinder.